Forensics Chapter 3 The Study of Hair

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Forensics Chapter 3 The Study of Hair

  1. Explain how hair can be considered class evidence as well as individual evidence.

Class evidence if alone and without follicle cells attached; if follicle cells are attached then DNA can be extracted and an individual may be identified

  1. We use a compound microscope in lab but explain why a comparison microscope would make analysis of the suspect and victim’s hair more advantageous.

You can place the two samples side- by -side for a better comparison.

  1. Explain how hair helps to regulate body temperature.

If the outside temperature is cold, muscles in the skin pull the hair strands upright, creating pockets that trap air. This trapped air provides a warm, insulating layer next to the skin. If the temperature outside is warm, the muscles relax and the hair becomes flattened against the body, releasing the trapped air.

  1. How many hair follicles do we have at birth? What percentage is found on our head?

At birth—5 million hair follicles; 2 percent are on the head

  1. What is the function of the sebaceous glands?

Secretes oil that helps keep the hair conditioned and is attached to the hair shaft

  1. ________is the protein that makes up the hair shaft. What is its importance to hair?

Keratin makes up the hair shaft and makes the hair strong and flexible.

  1. The networks of blood vessels that supply nutrients to help the hair grow are found in the__.

Papilla or Dermis

  1. What is the purpose of the nerves that surround the follicles?

Stimulate the erector muscle in response to changing environmental conditions.

  1. What is the function of the cuticle?

Outer layers which serve to protect the inner layers of the hair.

  1. The scales of the cuticle point toward older or younger hair growth.

Scales point toward the older hair growth

  1. The largest portion of the hair shaft is the ___ and contains ____that gives hair color.

largest portion is the cortex; melanin gives the hair color

  1. Describe or draw the 5 different medulla patterns present in humans.

a. continuous-one unbroken line of color

b. interrupted—pigmented line broken at regular intervals

c. fragmented or segmented-pigmented line unevenly spaced

d. solid- pigmented area filling both the medulla and the cortex

e. none-no separate pigmentation in the medulla

  1. Describe hair from the arms and legs.

Usually has a blunt tip, but may be frayed at the ends from abrasion

  1. Describe head hair in cross section.

Generally circular or elliptical in cross section

  1. Describe eyebrow and eyelash hairs.

Circular in cross section but often have tapering ends

  1. Describe body hair.

Oval or triangular in cross section but depends on whether the body region has been regularly shaved.

  1. Describe the structure of pubic hair in cross section.

Tends to be oval or triangular in cross section

  1. How many hairs do you typically lose each day?

Approximately 100 hairs per day

  1. Which phase of hair development do you think is most heavily impacted by cancer drugs?

Anagen phase which is period of growth

  1. Explain why bleaching of hair can be bad for the hairs.

Makes hair brittle and can disturb the scales on the cuticle

  1. How fast does anagen hair grow in a month?

1.3 centimeters per month or approximately 0.44mm per day

  1. Would hair be individual evidence if considering racial differences?

No ---there are generalities but may exist in people of different races.

  1. Explain how human and animal hair can be distinguished from each other considering the medulla and cuticle.

In animals the pigmentation is denser toward the medulla and in humans it is denser toward the cuticle.

Animal pigments are often found in sold masses called ovoid bodies and human hairs are usually one color along the length of the shaft but animal hairs may change color more abruptly

  1. Why is Locard’s principle mentioned again in this chapter?

Hair is considered trace evidence.

  1. What characteristics of hair are examined macroscopically?

Length, color and curliness

  1. What characteristics of hair are examined microscopically?

Pattern of medulla, pigmentation of the cortex and types of scales on the cuticle. Medullary index can be measured as well

  1. What is fluorescence and why is this an important tool in examining hair?

Absorption of light and then reemitting the light in a different color.

Hair that has been treated with dyes and other treatments will emit different colors

  1. What substances can hair be tested for?

Chemicals that skin can absorb can become incorporated into hair as well. Ingested toxins such as arsenic, lead and drugs can be detected by chemical analyses too .

  1. Identify 5 elements of the 14 that can be identified when using Neutron Activation Analysis.

Antimony, argon, bromine, copper, gold, manganese, silver, sodium, zinc

Probability of two individuals having same concentration of nine different elements is about one in a million.

NAA involves bombarding hair in a nuclear reactor with high-energy neutrons. Different elements give off gamma radiation with different signals and these signals can be recorded and interpreted to determine concentrations of element in the sample.

  1. Does the Neutron Activation Analysis lend itself more to class or individual evidence?


  1. What is a follicular tag? What can be obtained from obtaining a hair with a follicle on it?

A hair containing the follicle. Blood and tissue may be analyzed. DNA may be studied as well as blood type.

  1. Does a follicular tag lend itself more to class or individual evidence?


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